Title: Compositional and Functional Alterations of HDL Over Ovarian Aging PROJECT SUMMARY This application is in response to the current NIA FOA: PA-17-088 Secondary Analyses of Existing Cohorts, Data Sets and Stored Biospecimens to use data and biospecimens from the Study of Women?s Health Across the Nation (SWAN) to address a critical question about clinical aging, i.e. how ovarian aging impacts the role of high-density lipoproteins (HDL) on risk for cardiovascular disease (CVD). Multiple historic epidemiologic studies reported an inverse association between high-density lipoprotein cholesterol (HDL-C) and CVD, which suggests a direct cardio-protective function of HDL-C. However, recent results from Mendelian randomization studies and the failure of several HDL-C raising agents to reduce CVD risk, cast doubt on a cardio-protective function of HDL-C . As women traverse menopause there appears to be a switch in the direction of the association between HDL-C and CVD risk, with higher HDL-C level being associated with lower CVD risk before menopause and with higher CVD risk after menopause. HDL is a family of heterogeneous subclasses that vary in physico-chemical composition and function. HDL-C only measures the cholesterol load of HDL particles and therefore may not reflect changes in HDL composition and function that could accompany ovarian aging. Metrics of HDL composition and function provide a better ability to reflect the athero-protective features of HDL than HDL-C. Biological changes in these novel metrics of HDL have not been characterized over ovarian aging leading to uncertainty about the impact that the menopausal transition (MT) may have on HDL athero-protective capacity. The MT is a phase of life when women experience an acceleration of subclinical CVD. It is critical to fully understand the nature of the biological changes in HDL that accompany ovarian aging in midlife women. In response to the current NIA FOA: PA-17-088, the current application aims to 1) characterize changes in HDL composition and function over the MT, and assess how changes in HDL composition impact changes in HDL function in women at midlife; 2) evaluate the impacts of hormonal, metabolic and inflammatory marker changes on HDL composition and function changes over the MT; and to explore associations of changes in HDL composition and function with subclinical CVD progression in midlife women and to assess potential pathways. Frozen specimens from women participated in SWAN, a longitudinal study of ovarian aging, will be used to repeatedly measure 1) nuclear magnetic resonance HDL subclasses; 2) HDL content of phospholipids and triglycerides; and 3) the ability of HDL particles to promote cholesterol transport from peripheral cells (HDL-cholesterol efflux capacity), a key cardio-protective function of HDL, over the MT. The combination of the incomparable longitudinal menopause cohort (SWAN) and the comprehensive proposed panel of well-developed HDL composition and function metrics will significantly enhance our understanding of the complex biological changes in HDL over ovarian aging and how these changes could impact early markers of CVD and thus contribute to CVD development in aging women.